Tiling Walls
Background Preparation
Walls to be tiled
After many years running tiling training courses “well 22 years as a matter of fact” I have heard many delegates say I am attending a plastering course soon to help out with background preparation when I’m tiling.
This is not a necessary skill for a tile fixer, there is nothing wrong with multi-skilled trade’s people but as I said it is not an “absolute” to your skill base.
The reason plastering is no great benefit to a practising tile fixer is the overall weakness of plaster finishes and slow dry/cure times.
If the wall you are about to tile is both un-even with lumps, bumps and hollows the fastest route would be to make good using a rapid setting tile adhesive, thus allowing tiling to proceed in just a few hours rather than the normal four week wait for plaster to cure and be sufficiently strong enough to carry the weight of the tiles.
Bearing in mind that fully cured plaster will only support 20 kg per square metre in weight where plasterboard will carry 32 kg, however modern building techniques still adopt the dry lining (dot & dab) method using plasterboard then skim finishing the boards with plaster before tiling takes place.
Plaster finish and weight of tiles was never such an issue in this country when your British tile shops stocked 150 mm x 150 mm tiles in the main, these tiles would only weigh some 15 kg including the weight of adhesive & grout. These days wall & floor tiles are leaving tile shop doors with only four tiles to the box weighing in at 30 kg before we even get them in the car boot “holding on to your aching back” therefore we really do need look hard at how we prepare our bathroom walls before hanging a potential disaster over the family’s naked body soaking in the bath.
Back to the preparation if walls are un-even and assuming the plaster background is a finish plaster and NOT bonding plaster. We can first prime the plaster using a product with properties like BALs (APD prime) but never PVA, “why you may ask” PVA will break down in water and as the tiling products are all water based we do not want a built in disaster.
Once primed and dry after 30 minutes (approx) we can take a suitable length straight edge “ideally an aluminium one” and place it against the wall to be prepared in all directions vertically, horizontally and diagonally you will start to see lumps and hollows that are better corrected at the preparation stage rather than using lashings of adhesive during the tiling project.
I always think that the removal of bumps makes sense rather than building out the rest of the wall to meet the point of the bumps in the wall.
If you choose to remove these humps and bumps by taking your hammer and chisel to the wall think what could be the outcome, the finish plaster and the newly applied primer will be chopped away leaving a dusty un-primed plaster backing maybe even the bonding plaster could present itself to you, and as mentioned earlier this is not a good background for tiles.
That said you may opt for the building out process, bringing the hollows level with the tip of the humps and bumps, if this is the case start by holding the straight edge in all directions and marking the low areas using a pencil draw circles to show where the hollows are, once you have identified these areas it’s now time to mix a small quantity of rapid setting tile adhesive and apply with a flat trowel inside the circles you marked and fill the area out by the depth required.
Once all areas have been filled sufficiently take the straight edge and moving it back and forth across the filled areas you may take some of the filling off if you have applied more than was necessary, don’t worry if this is the case as even a professional would apply more, then allow the straight edge guide the flatness your looking for.
You may need to follow this procedure two or three times to give you a flat background to receive your tiles.
Once you feel happy with your efforts allow the rapid set adhesive to dry (normally two to three hours) now the wall is ready for tiling, trowel adhesive either a dispersion adhesive (ready mixed) or continue using a cement based as the wall was protected with primer allowing you to use the adhesive of your choice without risk of ettringite formation in other words the growth of crystals this occurs when un-primed plaster and cement based adhesive meet.
If the tiles to be fixed are large tiles say 300mm x 300mm or greater these fall in to the category of large format tiles and will require a thick bed of adhesive this means that the adhesive choice must only be a cement based adhesive, cement based adhesive can dry and cure even at bed depths of 12 mm in isolated areas where your ready mixed bucket adhesives are restricted to a maximum bad depth of 3 mm thus not allowing us this option.
If Riley’s tiling tips service can help your tiling project further please feel free in asking your questions by email paul@professional-itt.com.
The products mentioned in this edition of Riley’s tiling tips are available by clicking the web site below.
www.trades-direct.co.uk
Trades direct offers you a helpline before you buy your tiling products, call between 8-00 am and 9-00 pm 7 days for professional help on 01782 566166
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